Heat oil in a large stockpot.,Gently saute onions and garlic until golden brown, being careful not to burn them.,Add mussels to pot along with beer, marinara sauce, salt, pepper, and pasta seasoning, and top off with fresh chopped tomatoes and fresh basil.,______,Remove mussels to serving platter, discarding any that do not open.,Spoon sauce around mussels and put extra sauce in a serving bowl to be used for dipping crusty bread or serving over a side of pasta.